Heat sensitive imaging element and a method for producing lithographic plates therewith

Abstract

According to the present invention there is provided a thermosensitive imaging element for obtaining a lithographic printing plate comprising on a hydrophilic surface of a support a layer comprising an organic metallic salt and in the same or an adjacent layer an organic reducing agent and a compound capable of converting light into heat, said organic metallic salt being reducible on heating by said reducing agent to an ink-accepting compound or to a compound which can react with a hydrophobizing agent to an ink-accepting compound, characterized in that said layer comprising an organic metallic salt comprises a hydrophobic binder in an amount between 0.00 g/m 2 and 0.25 g/m 2 and a hydrophilic binder in an amount between 0.00 g/m 2 and 5.00 g/m 2 .

We claim: 
     
       1. A thermosensitive imaging element for obtaining a lithographic printing plate comprising on a hydrophilic surface of a support a layer comprising an organic metallic salt and in the same or an adjacent layer an organic reducing agent and a compound capable of converting light into heat, said organic metallic salt being reducible on heating by said reducing agent to an ink-accepting compound or to a compound which can react with a hydrophobizing agent to an ink-accepting compound, wherein said layer comprising an organic metallic salt comprises a hydrophobic binder in an amount between 0.00 g/m 2  and 0.25 g/m 2  and a hydrophilic binder in an amount between 0.00 g/m 2  and 5.00 g/m 2 . 
     
     
       2. A thermosensitive imaging element according to claim 1 wherein said organic metallic salt is an organic silver salt. 
     
     
       3. A thermosensitive imaging element according to claim 1 wherein a layer, comprising physical developing nuclei is present contiguous to said hydrophilic surface of a support. 
     
     
       4. A thermosensitive imaging element according to claim 1 wherein said hydrophilic surface of a support is anodized aluminum or comprises a flexible support having thereon a cross-linked hydrophilic layer. 
     
     
       5. A thermosensitive imaging element according to claim 1 wherein said compound capable of converting light into heat is an infrared absorbing compound. 
     
     
       6. A method for preparing a lithographic plate comprising the following steps: image-wise or information-wise exposing to heat an imaging element according to claim 1 and   rinsing the exposed imaging element with an aqueous solution thereby removing the layers on said hydrophilic surface of a support and exposing the reduced organic metallic salt.   
     
     
       7. A method for preparing a lithographic plate comprising the following steps: image-wise or information-wise exposing an imaging element according to claim 5 to light which can be absorbed by said compound capable of converting light into heat and   rinsing the exposed imaging element with an aqueous solution thereby removing the layers on said hydrophilic surface of a support and exposing the reduced organic metallic salt.   
     
     
       8. A method for preparing a lithographic plate according to claim 7 wherein said irradiating is effected by a laser. 
     
     
       9. A method for preparing a lithographic plate according to claim 6 wherein the exposed and rinsed imaging element is treated with a solution comprising a hydrophobizing agent. 
     
     
       10. A method for preparing a lithographic plate according to claim 6 wherein said thermosensitive imaging element is rinsed after mounting the image-wise or information-wise exposed imaging element on a print cylinder of a printing press. 
     
     
       11. A method for preparing a lithographic plate according to claim 6 wherein said thermosensitive imaging element is image-wise or information-wise exposed while being mounted on a print cylinder of a printing press.